NAME

krb5.conf - configuration file for Kerberos 5

SYNOPSIS

#include<krb5.h>

DESCRIPTION

The krb5.conf file specifies several configuration parameters for the
Kerberos 5 library, as well as for some programs.
The file consists of one or more sections, containing a number of
bindings. The value of each binding can be either a string or a list of
other bindings. The grammar looks like:
file:
/* empty */
sections
sections:
section sections
section
section:
’[’ section_name ’]’ bindings
section_name:
STRING
bindings:
binding bindings
binding
binding:
name ’=’ STRING
name ’=’ ’{’ bindings ’}’
name:
STRING
STRINGs consists of one or more non-whitespace characters.
STRINGs that are specified later in this man-page uses the following
notation.
boolean
values can be either yes/true or no/false.
time
values can be a list of year, month, day, hour, min, second.
Example: 1 month 2 days 30 min. If no unit is given, seconds
is assumed.
etypes
valid encryption types are: des-cbc-crc, des-cbc-md4, des-cbc-
md5, des3-cbc-sha1, arcfour-hmac-md5, aes128-cts-hmac-sha1-96,
and aes256-cts-hmac-sha1-96 .
address
an address can be either a IPv4 or a IPv6 address.
Currently recognised sections and bindings are:
[appdefaults]
Specifies the default values to be used for Kerberos
applications. You can specify defaults per application,
realm, or a combination of these. The preference order is:
1. applicationrealmoption
2. applicationoption
3. realmoption
4. option
The supported options are:
forwardable = boolean
When obtaining initial credentials, make the
credentials forwardable.
proxiable = boolean
When obtaining initial credentials, make the
credentials proxiable.
no-addresses = boolean
When obtaining initial credentials, request them
for an empty set of addresses, making the tickets
valid from any address.
ticket_lifetime = time
Default ticket lifetime.
renew_lifetime = time
Default renewable ticket lifetime.
encrypt = boolean
Use encryption, when available.
forward = boolean
Forward credentials to remote host (for rsh(1),
telnet(1), etc).
[libdefaults]
default_realm = REALM
Default realm to use, this is also known as your
“local realm”. The default is the result of
krb5_get_host_realm(localhostname).
clockskew = time
Maximum time differential (in seconds) allowed when
comparing times. Default is 300 seconds (five
minutes).
kdc_timeout = time
Maximum time to wait for a reply from the kdc,
default is 3 seconds.
v4_name_convert
v4_instance_resolve
These are described in the
krb5_425_conv_principal(3) manual page.
capath = {
destination-realm = next-hop-realm
...
}
This is deprecated, see the capaths section below.
default_cc_type = cctype
sets the default credentials type.
default_cc_name = ccname
the default credentials cache name. If you want to
change the type only use default_cc_type. The
string can contain variables that are expanded on
runtime. Only support variable now is %{uid} that
expands to the current user id.
default_etypes = etypes...
A list of default encryption types to use.
default_etypes_des = etypes...
A list of default encryption types to use when
requesting a DES credential.
default_keytab_name = keytab
The keytab to use if no other is specified, default
is “FILE:/etc/krb5.keytab”.
dns_lookup_kdc = boolean
Use DNS SRV records to lookup KDC services
location.
dns_lookup_realm = boolean
Use DNS TXT records to lookup domain to realm
mappings.
kdc_timesync = boolean
Try to keep track of the time differential between
the local machine and the KDC, and then compensate
for that when issuing requests.
max_retries = number
The max number of times to try to contact each KDC.
large_msg_size = number
The threshold where protocols with tiny maximum
message sizes are not considered usable to send
messages to the KDC.
ticket_lifetime = time
Default ticket lifetime.
renew_lifetime = time
Default renewable ticket lifetime.
forwardable = boolean
When obtaining initial credentials, make the
credentials forwardable. This option is also valid
in the [realms] section.
proxiable = boolean
When obtaining initial credentials, make the
credentials proxiable. This option is also valid
in the [realms] section.
verify_ap_req_nofail = boolean
If enabled, failure to verify credentials against a
local key is a fatal error. The application has to
be able to read the corresponding service key for
this to work. Some applications, like su(1),
enable this option unconditionally.
warn_pwexpire = time
How soon to warn for expiring password. Default is
seven days.
http_proxy = proxy-spec
A HTTP-proxy to use when talking to the KDC via
HTTP.
dns_proxy = proxy-spec
Enable using DNS via HTTP.
extra_addresses = address...
A list of addresses to get tickets for along with
all local addresses.
time_format = string
How to print time strings in logs, this string is
passed to strftime(3).
date_format = string
How to print date strings in logs, this string is
passed to strftime(3).
log_utc = boolean
Write log-entries using UTC instead of your local
time zone.
scan_interfaces = boolean
Scan all network interfaces for addresses, as
opposed to simply using the address associated with
the system’s host name.
fcache_version = int
Use file credential cache format version specified.
krb4_get_tickets = boolean
Also get Kerberos 4 tickets in kinit, login, and
other programs. This option is also valid in the
[realms] section.
fcc-mit-ticketflags = boolean
Use MIT compatible format for file credential
cache. It’s the field ticketflags that is stored
in reverse bit order for older than Heimdal 0.7.
Setting this flag to TRUE make it store the MIT
way, this is default for Heimdal 0.7.
[domain_realm]
This is a list of mappings from DNS domain to Kerberos realm.
Each binding in this section looks like:
domain = realm
The domain can be either a full name of a host or a trailing
component, in the latter case the domain-string should start
with a period. The trailing component only matches hosts that
are in the same domain, ie “.example.com” matches
“foo.example.com”, but not “foo.test.example.com”.
The realm may be the token ‘dns_locate’, in which case the
actual realm will be determined using DNS (independently of
the setting of the ‘dns_lookup_realm’ option).
[realms]
REALM = {
kdc = [service/]host[:port]
Specifies a list of kdcs for this realm.
If the optional port is absent, the
default value for the “kerberos/udp”
“kerberos/tcp”, and “http/tcp” port
(depending on service) will be used.
The kdcs will be used in the order that
they are specified.
The optional service specifies over what
medium the kdc should be contacted.
Possible services are “udp”, “tcp”, and
“http”. Http can also be written as
“http://”. Default service is “udp” and
“tcp”.
admin_server = host[:port]
Specifies the admin server for this
realm, where all the modifications to
the database are performed.
kpasswd_server = host[:port]
Points to the server where all the
password changes are performed. If
there is no such entry, the kpasswd port
on the admin_server host will be tried.
krb524_server = host[:port]
Points to the server that does 524
conversions. If it is not mentioned,
the krb524 port on the kdcs will be
tried.
v4_instance_convert
v4_name_convert
default_domain
See krb5_425_conv_principal(3).
tgs_require_subkey
a boolan variable that defaults to
false. Old DCE secd (pre 1.1) might
need this to be true.
}
[capaths]
client-realm = {
server-realm = hop-realm...
This serves two purposes. First the
first listed hop-realm tells a client
which realm it should contact in order
to ultimately obtain credentials for a
service in the server-realm. Secondly,
it tells the KDC (and other servers)
which realms are allowed in a multi-hop
traversal from client-realm to
server-realm. Except for the client
case, the order of the realms are not
important.
}
[logging]
entity = destination
Specifies that entity should use the specified
destination for logging. See the krb5_openlog(3)
manual page for a list of defined destinations.
[kdc]
database = {
dbname = DATABASENAME
Use this database for this realm. See
the info documetation how to configure
diffrent database backends.
realm = REALM
Specifies the realm that will be stored
in this database. It realm isn’t set,
it will used as the default database,
there can only be one entry that doesn’t
have a realm stanza.
mkey_file = FILENAME
Use this keytab file for the master key
of this database. If not specified
DATABASENAME.mkey will be used.
acl_file = PA FILENAME
Use this file for the ACL list of this
database.
log_file = FILENAME
Use this file as the log of changes
performed to the database. This file is
used by ipropd-master for propagating
changes to slaves.
}
max-request = SIZE
Maximum size of a kdc request.
require-preauth = BOOL
If set pre-authentication is required. Since krb4
requests are not pre-authenticated they will be
rejected.
ports = listofports
List of ports the kdc should listen to.
addresses = listofinterfaces
List of addresses the kdc should bind to.
enable-kerberos4 = BOOL
Turn on Kerberos 4 support.
v4-realm = REALM
To what realm v4 requests should be mapped.
enable-524 = BOOL
Should the Kerberos 524 converting facility be
turned on. Default is the same as
enable-kerberos4.
enable-http = BOOL
Should the kdc answer kdc-requests over http.
enable-kaserver = BOOL
If this kdc should emulate the AFS kaserver.
check-ticket-addresses = BOOL
Verify the addresses in the tickets used in tgs
requests.
allow-null-ticket-addresses = BOOL
Allow address-less tickets.
allow-anonymous = BOOL
If the kdc is allowed to hand out anonymous
tickets.
encode_as_rep_as_tgs_rep = BOOL
Encode as-rep as tgs-rep tobe compatible with
mistakes older DCE secd did.
kdc_warn_pwexpire = TIME
The time before expiration that the user should be
warned that her password is about to expire.
logging = Logging
What type of logging the kdc should use, see also
[logging]/kdc.
use_2b = {
principal = BOOL
boolean value if the 524 daemon should
return AFS 2b tokens for principal.
...
}
hdb-ldap-structural-object structuralobject
If the LDAP backend is used for storing principals,
this is the structural object that will be used
when creating and when reading objects. The
default value is account .
hdb-ldap-create-base creationdn
is the dn that will be appended to the principal
when creating entries. Default value is the search
dn.
enable-digest = BOOL
Should the kdc answer digest requests. The default
is FALSE.
digests_allowed = listofdigests
Specifies the digests the kdc will reply to. The
default is ntlm-v2.
[kadmin]
require-preauth = BOOL
If pre-authentication is required to talk to the
kadmin server.
password_lifetime = time
If a principal already have its password set for
expiration, this is the time it will be valid for
after a change.
default_keys = keytypes...
For each entry in default_keys try to parse it as a
sequence of etype:salttype:salt syntax of this if
something like:
[(des|des3|etype):](pw-salt|afs3-salt)[:string]
If etype is omitted it means everything, and if
string is omitted it means the default salt string
(for that principal and encryption type).
Additional special values of keytypes are:
v5 The Kerberos 5 salt pw-salt
v4 The Kerberos 4 salt des:pw-salt:
use_v4_salt = BOOL
When true, this is the same as
default_keys=des3:pw-saltv4
and is only left for backwards compatibility.
[password-quality]
Check the Password quality assurance in the info documentation
for more information.
check_library = library-name
Library name that contains the password
check_function
check_function = function-name
Function name for checking passwords in
check_library
policy_libraries = library1...libraryN
List of libraries that can do password policy
checks
policies = policy1...policyN
List of policy names to apply to the password.
Builtin policies are among other minimum-length,
character-class, external-check.

DIAGNOSTICS

Since krb5.conf is read and parsed by the krb5 library, there is not a
lot of opportunities for programs to report parsing errors in any useful
format. To help overcome this problem, there is a program
verify_krb5_conf that reads krb5.conf and tries to emit useful
diagnostics from parsing errors. Note that this program does not have
any way of knowing what options are actually used and thus cannot warn
about unknown or misspelled ones.